1. Field of the Invention
The present invention relates generally to the field of signal conditioning circuits, and more particularly to a linear variable differential transformer (LVDT) signal conditioner employing minimal excitation circuitry in association with a magnetic demodulation and excitation oscillator.
2. Background Information
An LVDT signal conditioner is a circuit for exciting an LVDT and detecting an output voltage that is proportional to the linear displacement of a magnetically enhanced rod of the LVDT. The LVDT is utilized to sense linear displacement(s) in servo control systems and is typically a part of the position control loop.
Various signal conditioning circuit topologies are known for producing a desired variable DC output voltage all of which are derived as a synchronous modulator-demodulator circuit pair. However, all of the LVDT signal conditioners known in the art require the use of an excitation oscillator to drive the primary circuit winding of the LVDT to provide carrier energy for modulation by the movable magnetic armature. The modulated carrier is an amplitude varying voltage that is induced on the secondary side of the LVDT and is synchronously demodulated to produce an output voltage proportional to the modulation amplitude (shaft displacement).
As position detection servo controls and the associated circuits become more complex, it is desirable to reduce power consumption of the detection circuits as well as the occupied volume and form factor variability of the components. An LVDT with low power (microwatt) signal conditioners are desirable as direct replacements in linear servo potentiometer control systems that are exposed to harsh vibration and temperature environments. It is also desirable to maintain optimum performance in high radiation environments by minimizing the use of susceptible semiconductor networks.
Therefore, it would be desirable to provide an LVDT signal conditioner that overcomes the above problems. The LVDT signal conditioner must be capable of being utilized in servo control positioning systems that employ a minimum of semiconductor networks and that are capable of providing servo position data within harsh vibration and temperature environments as those commonly found in launch vehicle and space systems.